In article . com,
"RHF" wrote:

On Jan 26, 9:21 am, "RHF" wrote:
On Jan 26, 6:11 am, David wrote:

On Fri, 26 Jan 2007 02:03:04 GMT, Telamon

wrote:
In article ,
David wrote:

On Thu, 25 Jan 2007 03:06:28 GMT, Telamon
wrote:

If you use a cable TV Balun you'll get a quick and dirty 4:1
transformer and a marked improvement.

http://www.radioshack.com/product/in...=2103912&cp=&s r=... gkw=matching+transformer&kw=matching+transformer&p arentPage=search

Those don't work well below 10 MHz. 15 MHz and higher they are OK.

How do you know?

I tested them.

What is the low frequency limiting component?- - I didn't go as far as
that.
- - This unit is made of a ferrite core and
- - a couple of very small value capacitors.
- - I would guess the core was the problem.
-
- I've reverse engineered a bunch of them.
- The ones with caps are very rare.

- Offhand - I can only come up with two reasons to
- put Capacitors in-side a Matching Transformer :
- 1 - To make it [Narrow] Band Specific {Tuned}
- 2 - To make it [Wide] Band Rejection {High -or- Low}

Example - Shortwave Baluns and Accessories
http://www.kintronic.com/site/subassemblies/baluns.asp
Kintronic Laboratories offers two types of Shortwave Baluns.
First is a discrete Discrete Component Shortwave Balun
with Tunable Capacitors to permit a 1:1 Match at any
Frequency in a Single Shortwave (HF) Band of operation.

New Longwire Balun 9:1 Transformer High Performer
-by- LowBander on eBay
http://cgi.ebay.com/_W0QQitemZ180078653482

About Baluns - What is the Best Balun ?
http://dxantennas.com/wst_page4.php

Snip

That would depend on the application like anything engineered. In
general the current type would be best for Hertzian antennas and I would
only use the voltage type on random/long wire Marconi type antennas.

--
Telamon
Ventura, California